Lesson 5.5.1

5.5.1 Plane polarisation and Huygens' construction Quiz: Pearson Edexcel Physics, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 5.5.1, Plane polarisation and Huygens' construction: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 5: Waves and Particle Nature of Light, written with Revision Ninja.

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The 20 questions

  1. What does it mean for a transverse wave to be plane polarised?

    • Its wavelength is the same in all media
    • Its oscillations rotate in a circle as it travels
    • Its oscillations are confined to a single plane
    • Its frequency is confined to a single value

  2. What does a polarising filter transmit?

    • All wavelengths of the incident light equally
    • Only the component of the oscillations parallel to its transmission axis
    • Only light whose frequency is above a threshold
    • Only light travelling in one direction along the filter

  3. Which phenomenon provides evidence that light is a transverse wave?

    • Dispersion
    • Polarisation
    • Diffraction
    • Refraction

  4. According to Huygens' principle, what does each point on a wavefront act as?

    • An absorber of the incident wave
    • A source of plane waves only
    • A source of secondary wavelets
    • A point of zero amplitude

  5. How is the new wavefront found using Huygens' construction?

    • As the sum of the amplitudes of the secondary wavelets
    • As the line perpendicular to all the wavelets
    • As the surface tangent to the secondary wavelets
    • As the line joining the centres of the wavelets

  6. When is diffraction most noticeable for a wave passing through a gap?

    • When the wavelength is much larger than the wave speed
    • When the gap width is much larger than the wavelength
    • When the gap width is comparable to the wavelength
    • When the wave is longitudinal rather than transverse

  7. Two polarisers have their transmission axes at 90 degrees to each other. What happens to unpolarised light passing through both?

    • The light changes to double its original frequency
    • All the light is transmitted, because polarisers add their effects
    • Almost no light is transmitted, because the second filter blocks the light polarised by the first
    • Half the light is transmitted, whatever the orientation

  8. Light passes through a polariser which is then rotated so that its transmission axis matches the plane of polarisation of the incident light. What is transmitted?

    • Half of the incident polarised light
    • None of the incident polarised light
    • All of the incident polarised light
    • Light at a different frequency

  9. Which is the better way to see that light is diffracted through a gap of width 5 micrometres, with wavelength 500 nm?

    • Both slits spread the light equally
    • Neither slit causes any spreading
    • A slit of width 0.5 mm, since it is larger
    • A slit of width 5 micrometres gives noticeable spreading, since width/wavelength = 10

  10. A student rotates a polarising filter in front of light from a blue sky and sees the transmitted intensity change. What does this show?

    • The sky light changes its colour as the filter rotates
    • The sky light is partly plane polarised
    • The sky light is unpolarised and has a fixed intensity
    • The sky light travels at varying speed

  11. A plane wavefront meets a single narrow slit whose width is comparable to the wavelength. What shape does the wave take beyond the slit?

    • A narrow straight beam with the same width as the slit
    • Wavefronts parallel to the slit in every direction
    • Semicircular wavefronts spreading out from the slit
    • Plane wavefronts unchanged in shape

  12. For a slit of width 2.0 micrometres and light of wavelength 500 nm, what is the ratio of slit width to wavelength?

    • 4.0
    • 2.5 x 10^-4
    • 4.0 x 10^3
    • 0.25

  13. Light of wavelength 400 nm passes a single slit of width 0.40 micrometres. What is the expected behaviour?

    • Ratio of width to wavelength is 0.001, so the spreading is strong
    • Ratio of width to wavelength is 1.0, so there is no diffraction
    • Ratio of width to wavelength is 100, so the spreading is strong
    • Ratio of width to wavelength is 1.0, so the spreading beyond the slit is strong

  14. A plane wavefront moves at speed v through a medium. How far does it advance in a time t, according to Huygens' construction?

    • t/v
    • v t
    • v/t
    • v t^2

  15. A wavefront in a medium moves at 300 m/s. What is the radius of the secondary wavelet emitted from a point on it after 0.010 s?

    • 0.030 m
    • 30 m
    • 3.0 m
    • 0.30 m

  16. A student says that polarisation of light by reflection shows light is a longitudinal wave. Which evaluation is correct?

    • Correct, because reflection occurs only for longitudinal waves
    • Incorrect, because polarisation is possible only for transverse waves, so it shows light is transverse
    • Incorrect, because light cannot be polarised at all
    • Correct, because polarisation shows light is a longitudinal compression

  17. Two polarisers are crossed at 90 degrees, and a third polariser is placed between them at 45 degrees. What effect does the middle polariser have on the transmitted light?

    • Only light at 45 degrees to the axes is transmitted
    • Some light is transmitted, because the middle polariser passes a component that the second polariser can transmit
    • No light is transmitted, because three polarisers always cancel
    • All light is transmitted, because the crossed pair cancels out

  18. A doorway of width 1.0 m is passed by sound of wavelength 2.0 m. Which best describes the diffraction?

    • Diffraction only for frequencies above 1 kHz
    • No diffraction, because sound is longitudinal
    • Strong diffraction, because the gap is smaller than the wavelength
    • Negligible diffraction, because the gap is much larger than the wavelength

  19. Why does a wave's wavelength change at a boundary while its frequency stays the same, according to Huygens' construction?

    • The wavelets change frequency as they slow down
    • The frequency is set by the boundary rather than by the source
    • The wavelets travel at the same speed, so the wavefront does not bend
    • Each wavelet is generated at the source frequency, but the wavelets travel at the new speed, so the wavelength changes

  20. A student claims that diffraction proves light is transverse. Which evaluation is correct?

    • Incorrect, because light cannot diffract at all
    • Correct, because diffraction needs oscillations perpendicular to the direction of travel
    • Incorrect, because diffraction occurs for both transverse and longitudinal waves, so only polarisation shows light is transverse
    • Correct, because diffraction only occurs for transverse waves

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